The Determination of Urinary Oxypurines as Markers of Gastrointestinal Tumors

Plasma levels and urinary excretion of oxypurines – hypoxanthine and xanthine – were evaluated by reverse-phase high-pressure liquid chromatography in 13 patients affected by gastric tumors and in 19 colorectal tumor-bearing patients. Preliminary results indicate higher values of urinary xanthine and an increase in the xanthine/hypoxanthine ratio in cancer patients. The increase was not generalized to all subjects, and did not appear related either to the stage of the disease or to CEA values. The limits within which the determination of urinary oxypurines can be employed as a tumor marker are discussed.

[A case of Xanthinuria in a patient with marked hypouricemia]

Xanthinuria is a rare autosomal recessive disorder associated with a deficiency of xanthine oxidoreductase (XOR), which normally catalyzes the conversion of hypoxanthine to uric acid. The effects of this deficit are an elevated concentration of hypoxanthine and xanthine in the blood and urine, hypouricemia, and hypouricuria. The deficit in XOR can be isolated (type I xanthinuria) or associated with a deficit in aldehyde oxidase (type II xanthinuria) and sulfite oxidase (type III xanthinuria). While the first two variants have a benign course, are often asymptomatic (20%), and clinically indistinguishable, type III xanthinuria is a harmful form that leads to infant death due to neurological damage. The clinical symptoms (kidney stones, CKD, muscle and joint pain, peptic ulcer) are the result of the accumulation of xanthine, which is highly insoluble, in the body fluids. We describe a case of type I xanthinuria in a 52-year-old woman who presented with hypouricemia, hypouricuria and kidney stones. The diagnosis was based on purine catabolite levels in urine and serum measured by 3 nonroutine methods: high-pressure liquid chromatography, mass spectrometry, and magnetic resonance imaging. To identify the type of xanthinuria the allopurinol test was used. We believe that these tests will facilitate the diagnosis of xantinuria especially in asymptomatic patients without the need for a biopsy of the liver or intestines, which is useful only for scientific purposes.

Plasma concentrations and urinary excretion of purine bases (uric acid, hypoxanthine, and xanthine) and oxypurinol after rigorous exercise

To investigate the effects of exercise on the plasma concentrations and urinary excretion of purine bases and oxypurinol, we performed 3 experiments with 6 healthy male subjects. The first was a combination of allopurinol intake (300 mg) and exercise (VO2max, 70%) (combination experiment), the second was exercise alone (exercise-alone experiment), and the third was allopurinol intake alone (allopurinol-alone experiment). In the combination experiment, exercise increased the concentrations of purine bases and noradrenaline in plasma, as well as lactic acid in blood and the urinary excretion of oxypurines, whereas it decreased the urinary excretion of uric acid and oxypurinol as well as the fractional excretion of hypoxanthine, xanthine, uric acid, and oxypurinol. In the exercise-alone experiment, exercise increased the concentrations of purine bases and noradrenaline in plasma, lactic acid in blood, and the urinary excretion of oxypurines, whereas it decreased the urinary excretion of uric acid and fractional excretion of purine bases. In contrast, in the allopurinol-alone experiment, the plasma concentration, urinary excretion, and fractional excretion of purine bases and oxypurinol remained unchanged. These results suggest that increases in adenine nucleotide degradation and lactic acid production, as well as a release of noradrenaline caused by exercise, contribute to increases in plasma concentration and urinary excretion of oxypurines and plasma concentration of urate, as well as decreases in urinary excretion of uric acid and oxypurinol, along with fractional excretion of uric acid, oxypurinol, and xanthine. In addition, they suggest that oxypurinol does not significantly inhibit the exercise-induced increase in plasma concentration of urate.

Ketamine Sedation During Spinal Anesthesia for Arthroscopic Knee Surgery Reduced the Ischemia-Reperfusion Injury Markers

We studied the effect of ketamine sedation on oxidative stress during arthroscopic knee surgery with tourniquet application by determining blood and tissue malonyldialdehyde (MDA) and hypoxanthine (HPX) levels. Thirty ASA I-II patients undergoing arthroscopic knee surgery with tourniquet were randomly divided into two groups. Spinal anesthesia induced with 12.5 mg bupivacaine was administered to all patients. In the ketamine group, after IV administration of 0.01 mg/kg midazolam, a continuous infusion of ketamine (0.5 mg . kg(-1) . h(-1)) was used until the end of surgery whereas the placebo group received a volume-equivalent placebo infusion. Ramsey Sedation Scale (RSS) was used for assessing the sedation level. Venous blood and synovial membrane tissue samples were obtained before ketamine infusion, at 30 min of tourniquet ischemia, and at 5 min after tourniquet deflation for MDA and HPX measurements. Tissue MDA and HPX levels were significantly less in the ketamine group than the control group after reperfusion. RSS scores were higher in the ketamine group without any adverse effect. We conclude that ketamine sedation attenuates lipid peroxidation markers in arthroscopic knee surgery with tourniquet application.

Newborn piglets with meconium aspiration resuscitated with room air or 100% oxygen

We investigated whether newborn piglets exposed to hypoxemia and severe meconium aspiration could be reoxygenated with room air as efficiently as with 100% O(2). Twenty-one 2- to 5-d-old piglets were randomly divided into three groups: 1) the room air group: hypoxemia, meconium aspiration, and reoxygenation with room air (n = 8); 2) the O(2) group: hypoxemia, meconium aspiration, and reoxygenation with 100% O(2) (n = 8); and 3) the control group: meconium aspiration, and reoxygenation with room air (n = 5). Hypoxemia was induced by ventilation with 8% O(2) until the mean blood pressure reached <20 mm Hg or the base excess reached <-20 mM. At this point, reoxygenation was started with either room air or 100% O(2). Three milliliters per kilogram of meconium 110 mg/mL was instilled into the trachea immediately before the start of reoxygenation. The O(2) tension in arterial blood was significantly lower in the room air group; at 5 min of reoxygenation it was 9.1 +/- 0.5 kPa versus 43.5 +/- 6 kPa in the O(2) group (p < 0.05). At 5 min of reoxygenation the tidal volume per kilogram was 12.1 +/- 0.7 mL/kg in the room air group and 13.1 +/- 0.9 mL/kg in the O(2) group (NS). There were no significant differences between the room air and the O(2) groups during 120 min of reoxygenation in mean arterial blood pressure, pulmonary arterial pressure, cardiac index, base excess, or plasma hypoxanthine. In conclusion, hypoxic newborn piglets with meconium aspiration were found to be reoxygenated as efficiently with room air as with 100% O(2).

Metabolism of intravenously administered high-dose 6-mercaptopurine with and without allopurinol treatment in patients with non-Hodgkin lymphoma

PURPOSE

We investigated the metabolism of high dose 6 mercaptopurine (HD-6MP) infusions and its influence on the metabolism by allopurinol, an inhibitor of xanthine oxidase, the enzyme that catabolizes 6MP into thioxanthine and thiouric acid.

PATIENTS AND METHODS

Nine patients (aged 2-11 years) with non-Hodgkin lymphoma (NHL) were treated with HD-6MP (1300 mg/m(2).24h) within a therapeutic window after diagnosis. Four patients received oral allopurinol (200 mg/m(2).day) to prevent urate nephropathy, and five did not. Plasma and RBC were isolated before and 4, 20, 24, 28, and 48h after the start of the infusion. All measurements were performed with HPLC.

RESULTS

Considerable variations were found in the plasma levels of 6MP, thioxanthine, and thiouric acid and of RBC-MeTIN levels. 6MP-riboside was not detectable, and MeMP and MeMPR levels were <1.3 muM in the plasma. In general, 6MP, thioxanthine, and MeMP levels in plasma were higher, and thiouric acid plasma levels and RBC-MeTIN levels were lower in the patients treated with allopurinol compared to those who did not receive allopurinol.

CONCLUSIONS

6MP is extensively metabolized in patients with NHL treated with HD-6MP. Thiopurine methylation, at the levels of nucleotide, nucleoside, and base, is an important metabolic pathway after HD-6MP. Co-administration of allopurinol can result in both a decreased catabolism and anabolism of 6MP compared to treatment with HD-6MP alone. This observation may have consequences for the therapeutic efficacy and toxic effects of 6MP in combination with allopurinol.

Ammonia response to exercise in patients with congestive heart failure

OBJECTIVE

To assess energy depletion in skeletal muscle in patients with congestive heart failure by measuring blood purine metabolites during exercise and, at the same time, determine the implications of the ammonia response to exercise in these patients.

SETTING

Tottori University Hospital, Yonago, Japan.

PATIENTS

49 heart failure patients (New York Heart Association (NYHA) grades I-III) and 16 normal subjects.

MAIN OUTCOME MEASURES

Blood lactate, ammonia, and hypoxanthine levels were measured during exercise with expired gas analysis.

RESULTS

In normal exercising subjects as well as in each heart failure subgroup, the ammonia threshold was significantly higher than both the lactate threshold [control: 21.8 (SD 5.3) v 17.4 (3.3) ml/kg/min; NYHA class I: 18.9 (3.8) v 15.5 (2.6); class II: 14.8 (2.5) v 12.7 (2.4); class III: 13.5 (2.6) v 11.8 (2.5)] and the ventilatory threshold (P < 0.01). The difference between the ammonia and lactate thresholds was noted in all normal subjects and in all heart failure patients. The ammonia threshold, however, was significantly lower in heart failure patients than in normal subjects and it decreased with increasing NYHA class (P < 0.01). Maximum ammonia levels were lower in the heart failure group and decreased further with higher NYHA classifications [control: 198 (52) mg/dl; NYHA class I: 170 (74); class II: 134 (58); class III: 72 (15); P < 0.01]. There were significant correlations between maximum ammonia values and maximum lactate, oxygen consumption, and hypoxanthine levels (r = 0.74, 0.48, and 0.87, respectively; P < 0.001).

CONCLUSIONS

The ammonia threshold may reflect the onset of ATP depletion in exercising skeletal muscles, as opposed to the onset of anaerobic respiration. It seems therefore that energy depletion in skeletal muscles during exercise occurs after attaining the anaerobic threshold. Both aerobic and anaerobic capacities of skeletal muscle are reduced in patients with congestive heart failure.

[Urate production in a porcine model of myocardial ischemia-reperfusion]

OBJECTIVE

This study was designed to investigate urate production by swine hearts using an in vivo regionally ischemic-reperfused model.

ANIMALS AND METHODS

Ten female pigs underwent 60 minutes of myocardial ischemia by clamping of the left anterior descending artery and afterwards 120 minutes of reperfusion. Epicardial biopsies and blood samples from coronary sinus were taken before ligation, at the end of ischemic period and 5, 30, 60 and 120 minutes upon reperfusion.

RESULTS

During ischemia, tissue levels of ATP and ADP greatly declined with a subsequent increase in the concentration of AMP, inosine and hypoxanthine (33 +/- 12 vs 93 +/- 17, 26 +/- 8 vs 768 +/- 86 and 32 +/- 10 vs 219 +/- 26 nmol/g dry weight, p < 0.01 for each). Despite the great increase in the hypoxanthine levels, uric acid concentration remained constant (69 +/- 9 vs 32 +/- 12 nmol/g dry weight, NS). Hypoxanthine, xanthine and uric acid concentrations increased in blood samples obtained from the coronary sinus at the end of ischemic period (17.99 vs 31.03 nmol/ml, p < 0.01, 0.29 vs 1.45 nmol/ml, p < 0.05 and 1.20 vs 2.31 nmol/ml, p < 0.01 respectively) and were enhanced upon reperfusion (35.8 and 3.89 nmol/ml for hypoxanthine and uric acid respectively, p < 0.05) without any significant modifications in their concentrations at the arterial level.

CONCLUSION

These results demonstrate that the ischemic-reperfused swine heart produces urate probably outside the myocardium.

Erythrocyte nucleotides and blood hypoxanthine in patients with uremia evaluated immediately and 24 hours after hemodialysis

Using high-performance liquid chromatography, concentrations of erythrocyte adenine nucleotides and hypoxanthine were evaluated in patients undergoing regular acetate hemodialysis before dialysis, immediately following dialysis, and 24 hr after. It was shown that adenosine triphosphate concentration was maintained consistently high, not only just after hemodialysis but also 24 hr later. There was also no difference in concentration of mono- and diphosphates of adenosine. Hypoxanthine concentration decreased twofold after hemodialysis. However, it was still markedly higher than normal values. The level of hypoxanthine was maintained at the postdialysis level, 24 hr later. This suggests that hypoxanthine production could be stimulated during acetate dialysis.

Effect of amino acids on the excretions of purine bases and oxypurinol

To investigate whether or not amino acids affect the urinary excretion of purine bases and oxypurinol, a 12% amino acid solution was infused to 6 subjects who took allopurinol (300 mg) 6 h before the study. Amino acid infusion increased the urinary excretion and the fractional clearance of uric acid and oxypurinol and decreased the plasma concentration of oxypurinol. However, it affected neither the urinary excretion, the fractional clearance, the plasma concentration of oxypurines nor the plasma concentration of uric acid. These results indicate that amino acids affect the renal transport pathways of oxypurinol and uric acid but not those of oxypurines. In addition, it was suggested that the amino acid-induced increase in the urinary excretion of oxypurinol may be considered when allopurinol is administered to hyperuricemic patients with hypoproteinemia who have taken amino acids either orally or intravenously.

Responses of blood and plasma lactate and plasma purine concentrations to maximal exercise and their relation to performance in standardbred trotters

OBJECTIVE

To study whether end products of 2 pathways of anaerobic energy metabolism, lactate and purines, that accumulate in the blood after intense exercise indicate any relation to exercise performance.

DESIGN

Venous blood samples were taken within 1 and 15 minutes after a trotting race of 2,100 m.

ANIMALS

16 Clinically healthy Standardbred trotters.

PROCEDURE

Blood and plasma lactate concentrations were measured by enzymatic analyzer, and purines, uric acid and allantoin, were determined by high-performance liquid chromatography. The concentrations of metabolites were then correlated to racing time and individual performance indexes that are annually calculated from the percentage of winnings, placings, and starts rejected, average earnings per start, and the racing record.

RESULTS

Blood lactate concentration immediately and calculated cell lactate concentration immediately and 15 minutes after the race correlated positively (P < 0.05 to P < 0.01) with the individual performance indexes. Plasma lactate concentration was not correlated to the individual performance indexes. Uric acid concentration, immediately and 15 minutes after the race, was negatively correlated (P < 0.05) to the individual performance indexes, and a positive relation (P < 0.05) was found between the highest concentration of uric acid and the racing time. Concentration of allantoin immediately or 15 minutes after the race did not have any significant correlation to the individual performance indexes.

CONCLUSIONS

Accumulation of lactate in the blood, which was greater in the superior performing horses, may prove to be an useful predictor of anaerobic capacity. The results also indicate that the loss of purine nucleotides was less in the superior performing horses, although further studies are needed to confirm this.

Regional generation of free oxygen radicals during cardiopulmonary bypass in children

Studies on free radical generation during cardiopulmonary bypass have focused mainly on the heart and the lungs. However, low pumping pressure, nonpulsatile perfusion, and hypothermia affect the entire circulation, resulting in decreased splanchnic blood flow, increased intestinal permeability, and endotoxemia. To evaluate regional phenomena, we studied 16 children undergoing cardiopulmonary bypass. Free radical production, granulocyte activation, and hypoxanthine metabolism were assessed separately in the circulations drained by the inferior and superior venae cavae, as well as in the oxygenator. Three minutes after the onset of cardiopulmonary bypass, significant gradients between the inferior vena cava and the arterial line of the oxygenator existed in malondialdehyde (+0.60 +/- 0.12 mumol/L, lactoferrin (+18.21 +/- 7.65 micrograms/L), myeloperoxidase (+53.75 +/- 16.50 micrograms/L), hypoxanthine (-0.62 +/- 0.15 mumol/L), and urate (+8.87 +/- 4.03 mumol/L). These gradients decreased in parallel with decreasing body temperature. Except for a transient gradient in malondialdehyde at 3 minutes after the onset of cardiopulmonary bypass (+0.23 +/- 0.08 mumol/L), no changes were detected between the superior vena cava and the arterial line. In the oxygenator, granulocyte activation was observed only after aortic declamping. We conclude that during cardiopulmonary bypass, significant free radical generation, granulocyte activation, hypoxanthine elimination, and urate production take place in the region drained by the inferior vena cava. In the oxygenator, granulocyte activation occurs only after aortic declamping.

Simultaneous determination of guanine, uric acid, hypoxanthine and xanthine in human plasma by reversed-phase high-performance liquid chromatography with amperometric detection

A reversed-phase high-performance liquid chromatographic method with amperometric detection is described for the separation and quantification of uric acid, guanine, hypoxanthine and xanthine. The isocratic separation of a standard mixture of the compounds was achieved in 5 min on a Spherisorb 5 C18 reversed-phase column, with a mobile phase of NaH2PO4 (300 mmol dm-3, pH 3.0)-methanol-acetonitrile-tetrahydrofuran (97.8 + 0.5 + 1.5 + 0.2). Uric acid, guanine, hypoxanthine and xanthine were completely separated, with detection limits in the range 2-20 pmol per injection. The effect of pH and the composition of the mobile phase on the separation are described. The hydrodynamic voltammograms of these compounds were recorded at a glassy carbon electrode. The linear range of the calibration graph for each compound was: uric acid, 1-5000 mumol dm-3; guanine, 0.5-2000 mumol dm-3; hypoxanthine, 0.1-500 mumol dm-3 and xanthine, 0.5-5000 mumol dm-3. The within- and between-day precision was good. The uric acid and hypoxanthine content in human plasma was measured using the proposed method. Good recoveries of uric acid (97.9-103%), hypoxanthine (98.0-99.2%), guanine (96.0-98.3%) and xanthine (96.0-102%) were obtained from human plasma. The results of electrochemical detection were in good agreement with those of UV detection.

Randomised controlled trial of allopurinol prophylaxis in very preterm infants

Allopurinol, an inhibitor of xanthine oxidase (an enzyme capable of generating superoxide radicals following hypoxiaischaemia), was investigated in preterm infants to determine its ability to prevent the complications of neonatal intensive care which may be associated with oxidative injury. Four hundred infants of between 24 and 32 weeks' gestation were randomly allocated to receive enteral allopurinol (20 mg/ml) or an equivalent dose of placebo for seven daily doses. At admission, plasma hypoxanthine concentrations were significantly higher in infants who subsequently developed periventricular leucomalacia (PVL), bronchopulmonary dysplasia (BPD), or retinopathy of prematurity (ROP), but there was no difference in the primary endpoint (PVL) between the treated and control groups. The failure of allopurinol prophylaxis in this group of infants is probably related to the complex nature of the pathological processes and to the timing of treatment. If oxidant injury is an important mechanism of cellular injury in these preterm infants, an alternative biochemical modulator would be required, or a combination of agents might be effective.

Skeletal muscle metabolism during short duration high-intensity exercise: influence of creatine supplementation

Seven male subjects performed repeated bouts of high-intensity exercise, on a cycle ergometer, before and after 6 d of creatine supplementation (20 g Cr H2O day-1). The exercise protocol consisted of five 6-s exercise periods performed at a fixed exercise intensity, interspersed with 30-s recovery periods (Part I), followed (40 s later) by one 10 s exercise period (Part II) where the ability to maintain power output was evaluated. Muscle biopsies were taken from m. vastus lateralis at rest, and immediately after (i) the fifth 6 s exercise period in Part I and (ii) the 10 s exercise period in Part II. In addition, a series of counter movement (CMJ) and squat (SJ) jumps were performed before and after the administration period. As a result of the creatine supplementation, total muscle creatine [creatine (Cr) + phosphocreatine (PCr)] concentration at rest increased from (mean +/- SEM) 128.7 (4.3) to 151.5 (5.5) mmol kg-1 dry wt (P < 0.05). This was accompanied by a 1.1 (0.5) kg increase in body mass (P < 0.05). After the fifth exercise bout in Part I of the exercise protocol, PCr concentration was higher [69.7 (2.3) vs. 45.6 (7.5) mmol kg-1 dry wt, P < 0.05], and muscle lactate was lower [26.2 (5.5) vs. 44.3 (9.9) mmol kg-1 dry wt, P < 0.05] after vs. before supplementation. In Part II, after creatinine supplementation, subjects were better able to maintain power output during the 10-s exercise period (P < 0.05). There was no change in jump performance as a result of the creatine supplementation (P > 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Capillary electrophoresis as a clinical tool. Determination of organic anions in normal and uremic serum using photodiode-array detection

We report the use of free solution capillary electrophoresis to identify and quantify low-molecular-mass compounds found in normal and uremic serum as well as in hemodialysate fluid. The method reported provides a multicomponent analysis, allowing a single-step screening for more than 19 metabolites in less than 16 min. Serum samples from healthy individuals and from patients who have been diagnosed with chronic renal failure are analyzed using a borate buffer system at pH 9.0, and an extended light path capillary. Several ionic sample constituents are identified by electrophoretic mobility, UV spectra, and spiking with authentic standards. An analysis of the relative concentration of several metabolites, including hypoxanthine, pseudouridine, hippuric acid, and uric acid is presented. Each of these four metabolites is found in both normal and uremic serum samples (limits of detection 1 to 6 microM). Moreover, each of these metabolites is present at significantly elevated levels in uremic patients. The method reported is shown to have promising clinical utility for profiling serum sample constituents, and for quantitative determination of a few important metabolites.

Creatine and its application as an ergogenic aid

Phosphocreatine (PCr) availability is likely to limit performance in brief, high-power exercise because the depletion of PCr results in an inability to maintain adenosine triphosphate (ATP) resynthesis at the rate required. It is now known that the daily ingestion of four 5-g doses of creatine for 5 days will significantly increase intramuscular creatine and PCr concentrations prior to exercise and will facilitate PCr resynthesis during recovery from exercise, particularly in those individuals with relatively low creatine concentrations prior to feeding. As a consequence of creatine ingestion, work output during repeated bouts of high-power exercise has been increased under a variety of experimental conditions. The reduced accumulation of ammonia and hypoxanthine in plasma and the attenuation of muscle ATP degradation after creatine feeding suggest that the ergogenic effect of creatine is achieved by better maintaining ATP turnover during contraction.

Xylitol-induced increase in the concentration of oxypurines and its mechanism

We investigated the effect of xylitol on the plasma concentration and the urinary excretion of purine bases, 5-hydroxypyrazinamide and 5-hydroxypyrazinoic acid in subjects who had ingested pyrazinamide (60 mg/kg weight). One liter of 10% xylitol was infused intravenously over 2 hours to 5 subjects to whom pyrazinamide had been administered 10 hours before. Xylitol increased the plasma concentration of uric acid, hypoxanthine and xanthine, the urinary excretion of hypoxanthine and a ratio of lactic acid/pyruvic acid in blood, while it decreased the plasma concentration and the urinary excretion of inorganic phosphate, 5-hydroxypyrazinamide and 5-hydroxypyrazinoic acid. These results suggested that in addition to an increase in purine degradation by xylitol, xylitol-induced increase in the cytosolic NADH inhibited xanthine dehydrogenase activity in the liver and the small intestine.

Intrauterine exposure to cocaine increased plasma ANP (atrial natriuretic peptide) but did not alter hypoxanthine concentrations in the sheep fetus

To assess the effects of cocaine, administered to the ewe, on the secretion of atrial natriuretic peptide (ANP), Plasma Renin Activity (PRA) and hypoxanthine in the fetus we studied 6 chronically cannulated sheep fetuses late in gestation. The ewe was given an intravenous injection of cocaine (2 mg/kg). Maternal and fetal arterial blood samples were withdrawn prior to the injection and at 2, 5, 10, 15, 45 and 60 min after the injection for the measurement of ANP, PRA and hypoxanthine. Fetal arterial blood pressure (MAP), plasma ANP and protein levels increased and pH and pO2 decreased after cocaine was administered to the ewe. Fetal plasma hypoxanthine and PRA did not change. These results suggest that cocaine administration to the ewe is associated with fetal hypertension, hypoxemia and acidemia all of which may serve as stimuli for the secretion of ANP.

Markers of acute and chronic asphyxia in infants with meconium-stained amniotic fluid

OBJECTIVE

Cord blood pH, lactate, hypoxanthine, and erythropoietin levels have all been used as markers of either acute or chronic asphyxia. We sought to determine whether these index values were significantly different in infants with or without meconium-stained amniotic fluid.

STUDY DESIGN

Fifty-six pregnant women in spontaneous labor at term were divided into two groups on the basis of the presence or absence of meconium-stained amniotic fluid. All meconium-stained fluid was centrifuged, and the volume percentage of particulate matter (i.e., meconium) was recorded. Umbilical artery blood and mixed arterial and venous cord blood were obtained at each delivery. Lactate, hypoxanthine, and erythropoietin levels were measured. Statistical analysis included Student t test and rank sum statistics where appropriate. Normal and Spearman correlation coefficients were also used.

RESULTS

There were no significant differences in mean umbilical artery pH (7.26 +/- 0.06 vs 7.25 +/- 0.10), lactate levels (32.8 +/- 10 mg/dl vs 30.4 +/- 14.2 mg/dl), and hypoxanthine levels (13.4 +/- 6.7 mumol/L vs 14.0 +/- 6.0 mumol/L) in newborns with meconium (n = 28) compared with controls (n = 28). Erythropoietin levels were significantly greater in newborns with meconium (median 39.5 mIU/ml vs 26.8 mIU/ml, p = 0.039). There was no correlation between the amount of particulate matter and any marker of asphyxia.

CONCLUSIONS

There was no correlation between markers of acute asphyxia (i.e., umbilical artery blood pH, lactate, or hypoxanthine) and meconium. However, erythropoietin levels were significantly elevated in newborns with meconium-stained amniotic fluid. This latter marker may better correlate with chronic asphyxia.

Breakdown of adenine nucleotides, formation of oxygen free radicals, and early markers of cellular injury in endotoxic shock

OBJECTIVE

To study the influence of shock on muscle and plasma adenine nucleotide and creatine pools and their metabolites, and to identify early markers of cellular injury in shock.

SETTING

Surgical research laboratory, Kuwait and UAE.

DESIGN

Experimental study.

MATERIAL

19 New Zealand rabbits.

INTERVENTIONS

15 rabbits were injected with Escherichia coli endotoxin, and an additional 4 rabbits acted as controls.

MAIN OUTCOME MEASURES

Blood and muscle energy metabolites, platelet count, arterial blood gas tensions, and arterial pressure were followed until the animals died.

RESULTS

Five minutes after injection of endotoxin muscle ATP, creatine phosphate, and total adenine purine concentration decreased. This decrease was later reversed, but again decline to a critical level in the terminal phase. Loss of the muscle creatine pool indicated cellular damage after 3 hours. Plasma hypoxanthine, creatine, and lactate concentrations increased continuously throughout the study.

CONCLUSION

Hypoxanthine formation is a possible source of oxygen free radicals in shock. The rise of hypoxanthine, creatine, and lactate concentrations in plasma during septic shock may reflect early high energy nucleotide failure, membrane injury, and anaerobic metabolism, respectively.

Effects of oxygen radicals on cysteinyl leukotriene metabolism and pulmonary circulation in young pigs

The effects of oxygen radicals, generated by the hypoxanthine-xanthine oxidase (XO) system, on pulmonary circulation and release of cysteinyl-containing leukotrienes (LTs) were studied in pigs after XO infusion into the right atrium. A 2.3-fold increase in pulmonary vascular resistance (PVR) (p < 0.05 vs. baseline) and a 2.1-fold increase in LT release (p < 0.05 vs. baseline) was observed. Pretreatment with indomethacin and allopurinol attenauted the vascular response (p < 0.01 and p < 0.05 vs. XO), and the LT release was inhibited by allopurinol and catalase (p < 0.01 and p < 0.02 vs. XO). We conclude that oxygen radicals stimulate lipoxygenase metabolism. This coincides with the observed increase in PVR, however, no causal relationship can be derived from the data presented.